Process of separating hydrocarbon fractions



M rch 4.29 1927.

a D. PYzl-:L

I PROCESS OF SEPARATING HYDROCARBON FRACTIONS Filed Aug 25, 1925 Qin ESQ TTORNE'KS.

rPatented' Mar. 29, 19,27.

1,622,737 PATENT OFFICE.

DANIEL rYzEL, or PIEDNON'I, CALIFORNIA, AssIGNoN. To sIMPLEx REEINING Con- PANY, or saN FRANCISCO, CALIFORNIA, A CORPORATION OE CALIFORNIA.

PROCESS F BEPABATING HYDROCARBON rIFRAC'IIONS.

application ma august 2s, 1923. smal- No. 658,910.

My invention relates to the art of oil refining and particularly to the art of fractionating oil vapors.

In 'the art of oil refining an oil vapor is usually produced by the still, this vapor being made up of a complex series of hydrocarbons, the different hydrocarbons having various boiling points. F

It is an object of the present invention to .0 provide means whereby a hydrocarbon of definite characteristics can be separated from such a complex mixture.

It is 'further an objectto separate from a vapor containing a complexmixture of hy l5 drocarbons a condensate having 'a definite range of boiling points, and it is further-an object of this invention vto separate from such a condensate any hydrocarbons which may be entrained in the condensate as originally formed, and which have boiling points below 'the desired range.,x

Further objects and advantages will be made evident hereinafter.

`Referring to the drawing which is for I5, illustrative purposes only,

Fig. 1 is an elevation partly in section showing diagrammatically one form of" apparatus embodying my invention.

, Fig. 2 isa section on a plane .represented 0 'by the line 2-,2 of Fig. 1.

Fig. 3 is a 'section on a plane represented by the line 3&-3 of Fig. 1. Fig. 4 is a section on a' bythe line 4-4 of Fig. 1.

5 "In the form of the invention illustrated I use a dephlegmator 11, a rerun still 21, a

, cooler 31 and a pump 41. Vapor from an oil still, not shown, 1s delivered to the def phlegmatr "r11 through a pipe 12, the de- 0 phle ator consisting of a tight shell 13 in plane represented wh-ic are .placedpans 14 and 15. The' ans` 14 are smaller in diameter than the s ell, leaving'an annular o ening 16 therearound. The pans 15 fit tight y in the shell and have 5 a central opening 17. The .vapor entering the de hlegmator passes in a tortuous course around) the pans 14 and through the center of the pans 15, being finally withdrawn through a pipe 18 "and delivered to additional de hlegmators or condensers, not shown. (ibid condensate is delivered-into the top of the-dephlegmator through a pipe The cold condensate in its passage downwardly through the dephlegmator fills the pans 14 and 15, passing successively down from these pans and into the bottom, from which it is withdrawn through a pipe 19. In its passage through the dephlegmator the cooled condensate acts as both a cendensing and an absorbing medium, that is to say it acts upon the oil vapors to cool them, thereby causingthe higher boiling point frac.

tions to condense, and it also acts directly, especially in the cooler upper part of the dephlegmator, to absorb from the oil vapors certain of the lower boiling point vapors carried therein. On the other hand the hot vapors in the lower part of the dephlegmator tend Ito levaporate from the condensate part of the low boiling point oils; which are absorbed therein. The vaporsV condensed or absorbed add'to the volume of the condensate `andfthe mixture from the bottom of 'the dephlegmator 11 is carried through the pipe 19 to the rerun still 21.

This still consists of a tight shell 22 having false heads 23 therein,.between which tubes 24 extend. A large ortion of the hot condensate is delivered by means of a pipe 25V into the space Vat one end of the rerun still 21 outside one of the heads 23, this portion of the condensate flowing through the tubes 24 into a s ace at the opposite end of the rerun still an being taken off therefrom byy means of a pipe 32. The other smaller portion of the condensate isdeliveredthrough a pipe 26 to the space between the heads 23, flowing from left to right through" this ace, in which it is in contact with lthe outsi e of the tubes 24 through which the larger portion of the hot condensate is flowing. The inte- 4rior of the space between theheads 23 is 'divided into lseveral parts by partitions 2'?` which extend down into the liquid therein,

'forming separate vapor s aces from which independent vapor takeo s 28 lead to suitable condensers, not shown. Steam is supplied to these spaces through perforated pipes 20 and the level of the tained above the bottom of the partitions 27 iquid is mainby means of the pipe 29, which projects up linto the rerun still to the necessary height to accomplish this result. y The injection of steam through the perforated pipes 20 causes an evaporatlon from thev body of liquid in the rerun still, the vapors, consistin of the low boiling point fractions, being wit drawn f 65.. perature of vapors leaving the condenser byY through the pipes 28 so that the body of condensate in the stillA is freed of low boiling `point fractions. A.The evaporation .of these f. low boiling fractions. To prevent this, heat is supplied to the liquid in the rerun still by the tubes 24, through which the larger. Ypart of the hot condensate from the dephlegmator flows. After giving off part of its heat, through the tubes`24 to the liquid in the rerun still, this condensate is ,carried off by the pipe 32 to the cooler 31, this cooler having intermediate heads 33, between which tubes 34 extend. Cold water or another cooling medium is delivered to the space between the heads 33 by a pipe 35,'the heated cooling medium being lwithdrawn through the pipe 36. The function of the cooler 31 is to still further cool the condensate which is then forced by thepump 41 through the pipe 42 into the top of the dephlegmator.

A valve is provided in the pipe 26 for the p'urposeof regulating the proportion of the condensate delivered by the pipe 19 which will be passed through the pipe 26 into the central chamber, of the rerun still.

By the use of the dephlegmator 11, it is possible to separate from the vapor all of the condensate which will condense below a certain temperature. At the same time the condensate in the dephlegmator 11 must necessarily cont-ain Acertain fractions `which.

have a lower boiling point than the desired product. These vlowenboiling point fractions are re-evaporated in the rerun still and taken over by the pipes` 28 so .that the condensate delivered to the pipe 29 is free from these low' boiling point fractions which are,

however, valuable and which are saved and utilized for other purposes.y By( the use ofimy invention a condensate having a very vdefinite range of boiling points is -continuously delivered' throughf'the pipe ,29, cer- K tain other condensat'es having lower boiling points being delivered as vapors through the pipes 28. f v.

The'vapors delivered through the pipeI 12 from the still, not shown, to the dephleg- Ina-tor 11 consist at any instant of a complex mixture of hydrocarbon vapors, all of which vaporizebelow the still temperature and substantially none of whichfrequire a higher vaporizing temperature. This mixture delivered through the ipe 12 therefore consistsl of hydrocarbons oiling at a temperature below that of the still.

In the dephlegmator 11 a portion of the vapors are cooled and partly condensed by a circulating stream of cold condensate entering through the pipes/l2, the proportion so condensed being determined by the exittem- -ably below the exit temperature of the dephlegmator. These lighter vapors, in many cases, when condensed 'form products which are much more valuable Athan the condensate itself. For example, the condensate may be chiefly a heavy andrelatively low priced gasoil distillate and the lighter vapors absorbed may be gasoline having a considerably greater value. It is the purpose of the rerun still 21 to remove these lighter vapors from a part of the condensate equal in quantity to the condensate formed in the dephlegmator, p

This is accomplished by means of the heat alreadyin the ,liquid flowing fromthe dephlegmator 11 through the pipe 19.I A portion of this liquid Hows through the tubes 24 and a portion surrounds these tubes. Since it is desired to extract heat from the liquid inside the tubes, it is necessary that the temperature ofthe liquid outside the tubes be lowered. It` is obvious'that if it is desired to cause an evaporation from the liquid outside the tubes at this lower temperature, it will be necessary to lower the absolute pressure on this liquid, which could be done by means of a vacuum pump,'or to lower the partial pressure by the injection of steam, which is the expedient I adopt herein.

By injecting steam into the liquid outside the tubes 24, I not only agitate the liquid butA I also produce in the space above the liquid a mixture of steam and oil vapors, and thereby /fgreatly lower the partial 'pressure of the/,oil vapors. As a result I am able to evaporate from the liquid in the rerun still all the low boiling point vapors carried therein, this evaporation taking place at a temperature considerably below that of the li uid flowing through the pipe 19. l

ue to the reduction in thef partial oil vapor pressure inside the rerun still 21, which is due in turn to the presence of steam, I am able to evaporate such lovv7 boiling point vapors at this lower temperature, the vlatent heat of vaporization being supplied by heat conduction from theliquid in the tubes 24.

The function of the injected steam is solely the reduction of the partial oil vapor presi sure necessar to cause the jliquid to boil, notwithstanding vthe reduction in temperature caused by the evaporation of its lighter constituents. The temperature of the injected steam is, therefore, immaterial. If it is higherl than that of the oil, it will glve off a small amount of heat to this oil; if it is lower, it will be heated to the temperature of the oil, theheat required for this purpose ieng, supplied by the hotter oil inside the u es.

Preferably, the steam is supplied at about the same temperature as that of the li uid outside the tubes 24, which is determine by the evaporation of low boiling point vapors therefrom, and the `consequent extraction of heat therefrom. I v

By allowing the liquid to flow inside the rerun still 21 from left to right, as shown in Fig. 1 and subecting it to this evaporation under parta' ressure, I am able to distill therefrom substantially all the low boiling point hydrocarbons which are delivered asfvapor through the pipes 28, s o that ythe liquid finally withdrawn through the 4 by the use of the sensible heat carried in that part of the liquid delivered from the pipe 19 by the pipe 25 to the inside of the heating tubes.

This part of the liquid, after supplying the heat required in the rerun still, is then delivered by the pipe 32 to a cooler 31 Where it is further cooled, after which it is pumped back through the pipe li2-to the top of the dephlegmator as a cooling medium.

- ing the mixture of' vapors produced by saidv l claim as my invention:

1. A process of separating hydrocarbon fractions from a heated mixture of said fractions in a liquid state which comprises: lowering the partial vapor pressure on a portion 0i said mixture vby injecting therein vapor having a different vapor tension; supplying heat to said portion from the remainder of said mixture, said remainder being held under its initial vapor tension; and removinjection and heating. 2. A process of separating hydrocarbon `i'ractions from a heated mixture of said fractions in a liquid state which comprises: lowering the partial vapor pressure on a portion of said mixture by injecting steam therein; supplying heat to said portion from the remainder of said mixture, said remainder being held under its initial vapor ten-.

1- sion; and removing the mixture of vapors produced by said injection and hea-ting.V 3. A .process of separatiner a hydrocarbon fraction having definite boi ing point limits from a mixture of hydrocarbon vapors which` com rises: condensing from said vapors a con ensate; passing a portlon of said condensate at a temperature slightly below its initial boiling point at the pressure at which it is condensed into a space in which its partial pressure is sufficiently reduced to cause vaporization of light hydrocarbons therefrom; andsupplying a portion of the heat necessary to produce said vaporization byv conduction fromthe remainder of said condensate.

4. A process of separatin la hydrocarbon fraction having definite boi ing point limits from a mixture of hydrocarbon vapors which com rises: condensing from said vav pors a con ensate; passing a portion of said condensate at a temperature slightly below its initial boiling point at the pressure at which it is condensed into a space in which its partial pressure is suiciently reduced by the introduction of steam to cause vaporiza tion of light hydrocarbons therefrom; and sup lyinga portion ofthe heat necessary to pro uce said vaporization by conduction from the remainder of said condensate.

5. A process of separatin a hydrocarbon fraction having definite boi ing point limits from a mixture of hydrocarbon vapors which comprises; condensing from said vapors a condensate; passing a portion of said condensate at a temperature slightly below its initial boiling point at the pressure at which it is condensed yinto a space in which its partial pressure is sufficiently reduced to cause vaporizationl of llight hydrocarbons therefrom; supplying `a portion of the heat necessary to produce said vaporization by conduction from the remainder of said condensate; and passing saidI remainder back into direct` contact with said vapors.

6. A process of separating a hydrocarbon.

fraction having definite boiling point limits fromi a mixture of hydrocarbon vapors which comprises: condensing from said vapors a condensate; passing a portion of said condensate at a temperature slightly below its initial boiling point at the pressure atl densate; cooling said remainder; and passing sald remainder back into direct Contact with said vapors.

In testimony whereof, I have hereunto set my hand at San Francisco, California, this 16th dayl of August, 1923. t

. DANIEL PYZEL.

llt) 

